Don't enable HDCP again if it is active

ui/display/chromeos/display_configurator.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/display/chromeos/display_configurator.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 233 matching lines @@
         all_desired = request_it->second;
     }
 
     switch (it->display->type()) {
       case DISPLAY_CONNECTION_TYPE_UNKNOWN:
         return false;
       // DisplayPort, DVI, and HDMI all support HDCP.
       case DISPLAY_CONNECTION_TYPE_DISPLAYPORT:
       case DISPLAY_CONNECTION_TYPE_DVI:
       case DISPLAY_CONNECTION_TYPE_HDMI: {
-        HDCPState new_desired_state =
-            (all_desired & CONTENT_PROTECTION_METHOD_HDCP) ?
-                HDCP_STATE_DESIRED : HDCP_STATE_UNDESIRED;
-        if (!native_display_delegate_->SetHDCPState(*it->display,
-                                                    new_desired_state))
+        HDCPState current_state;
+        if (!native_display_delegate_->GetHDCPState(*it->display,

[dnicoara, 2014/09/19 15:57:53]

Would you mind adding a comment here to explain why this is necessary? I'm
afraid someone will try to optimize this out in a refactor.

[kcwu, 2014/09/23 05:43:22]

I am not sure what you mean. I added one more sentence in line 260. Please take
a look.

[dnicoara, 2014/09/23 13:35:44]

Awesome! I'm thinking something along the lines "Need to poll the driver for
updates since other applications may have updated the state". Something along
the lines of your explanation in message #6.

[kcwu, 2014/09/24 14:57:44]

Done.

+                                                    &current_state))
           return false;
+        bool current_desired = (current_state != HDCP_STATE_UNDESIRED);
+        bool new_desired = (all_desired & CONTENT_PROTECTION_METHOD_HDCP);
+        // Don't enable again if HDCP is already active.
+        if (current_desired != new_desired) {
+          HDCPState new_state =
+              new_desired ? HDCP_STATE_DESIRED : HDCP_STATE_UNDESIRED;
+          if (!native_display_delegate_->SetHDCPState(*it->display, new_state))
+            return false;
+        }
         break;
       }
       case DISPLAY_CONNECTION_TYPE_INTERNAL:
       case DISPLAY_CONNECTION_TYPE_VGA:
       case DISPLAY_CONNECTION_TYPE_NETWORK:
         // No protections for these types. Do nothing.
         break;
       case DISPLAY_CONNECTION_TYPE_NONE:
         NOTREACHED();
         break;
@@ skipping 679 matching lines @@
         return state_controller_->GetStateForDisplayIds(display_ids);
       }
     }
     default:
       NOTREACHED();
   }
   return MULTIPLE_DISPLAY_STATE_INVALID;
 }
 
 }  // namespace ui